Emergence without limits: The case of phonons

• Published in: Studies in History and Philosophy of Modern Physics Vol. 64; pp. 68 - 78
• Main Authors: Franklin, Alexander, Knox, Eleanor
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2018
• Subjects: Asymptotic limits; Emergence; Novel explanation; Phonons; Quasi-particles; Reduction; Novel explanation; Reduction; Asymptotic limits; Emergence; Phonons; Quasi-particles
• ISSN: 1355-2198; 1879-2502
• DOI: 10.1016/j.shpsb.2018.06.001

Recent discussions of emergence in physics have focussed on the use of limiting relations, and often particularly on singular or asymptotic limits. We discuss a putative example of emergence that does not fit into this narrative: the case of phonons. These quasi-particles have some claim to be emergent, not least because the way in which they relate to the underlying crystal is almost precisely analogous to the way in which quantum particles relate to the underlying quantum field theory. We offer an account of emergence which encompasses phonons, and argue both that emergence may thus be found in cases where the use of limits is not required, and that it provides a way of understanding cases that do involve limits. •Phonons are derived from the crystal lattice.•The derivation does not involve asymptotic limits or essential idealization.•Phonons are nonetheless emergent.•Therefore emergence is not always about limits.•In this case emergence results from a change of variables, abstraction and novel explanation.